Method for predicting the polishing characteristics and life-span of a soft polishing pad

ABSTRACT

A method for predicting the polishing characteristics and life-span of a soft polishing pad includes the steps of: (a) establishing a matching database by means of performing a series of dynamic analysis tests on a new soft polishing pad by a contact probe at different frequencies and under different loads and detecting the surface reaction of the new soft polishing pad, (b) performing a dynamic analysis test on a to-be-tested soft polishing pad by a contact probe at a predetermined frequency and under a predetermined load and detecting the surface reaction of the to-be-tested soft polishing pad, and (c) comparing the surface reaction data of the to-be-tested soft polishing pad with the matching database and predicting the polishing characteristics and life-span of the to-be-tested soft polishing pad subject to the comparison result. Subject to the aforesaid steps, the polishing characteristics and life-span of the to-be-tested soft polishing pad can be predicted without making an actual polishing test, thereby saving a large amount of time and cost.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to polishing technology and more particularly, to a method for predicting the polishing characteristics and life-span of a soft polishing pad.

2. Description of the Related Art

Polishing or lapping is a post processing process for the surface finishing of a precision workpiece to have the surface roughness and planarity of the precision workpiece be within a tolerable range. Using a polishing pad to perform a polishing process is one of the main surface finishing techniques.

Before entering the polishing process, a soft polishing pad having suitable polishing characteristics (such as surface roughness) is selected subject to the workpiece to be polished so that the best polishing efficiency and quality can be obtained.

In another word, knowing the polishing characteristics and life-span of a soft polishing pad and the effect of a polishing pad on different workpieces is the key point to select the right polishing pad.

However, the commonly adopted method of obtaining the data of the polishing characteristics of a polishing pad and predicting its life-span is to perform a large number of actual polishing tests. This method wastes much time and cost.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide a method for predicting the polishing characteristics and life-span of a soft polishing pad, which predicts the polishing characteristics and life-span of a polishing pad rapidly without any actual polishing test, thereby saving much time and cost.

To achieve this and other objects of the present invention, a method for predicting the polishing characteristics and life-span of a polishing pad includes the steps of: (a) preparing a new soft polishing pad having polishing characteristics that are known, and then performing a series of dynamic analysis tests to oscillate the new soft polishing pad by a contact probe at different oscillation frequencies and under different loads, and then detecting the surface reaction of the new polishing pad during every dynamic analysis test, and then using the tested data and the known polishing characteristics of the new soft polishing pad to establish a matching database; (b) preparing a to-be-tested soft polishing pad for polishing a predetermined workpiece and then performing a dynamic analysis test to oscillate the to-be-tested polishing pad at a predetermined oscillation frequency and under a predetermined load and then detecting the surface reaction of the to-be-tested polishing pad; and (c) comparing the surface reaction of the to-be-tested polishing pad with the data of the matching database to predicate the polishing characteristics and life-span of the to-be-tested polishing pad. Subject to the aforesaid steps, the polishing characteristics and life-span of the to-be-tested polishing pad can be predicted without making an actual polishing test, thereby saving a large amount of time and cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of a method for predicting the polishing characteristics and life-span of a soft polishing pad in accordance with the present invention.

FIG. 2 is a schematic drawing showing the operation status of step (A) of the method for predicting the polishing characteristics and life-span of a soft polishing pad in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a method for predicting the polishing characteristics and life-span of a soft polishing pad in accordance with the present invention includes the following steps (A)-(C).

In step (A), prepare a new soft polishing pad 11 of which the polishing characteristics are known, and then perform a series of dynamic analysis tests to oscillate the new polishing pad 11 at different oscillation frequencies and under different loads. According to the present preferred embodiment, the dynamic analysis tests are performed through a contact probe 12 subject to the use of a cam mechanism, piezoelectric device or any other means controllable to produce a cyclic stress F1 that is applied to the surface 111 of the new polishing pad 11 perpendicularly, thereby simulating the conditions in which surface asperities of different workpieces (wafer or metal surface) are moved over the surface of the polishing pad 11.

Further, the reaction of the surface 111 of the new polishing pad 11 is detected during every dynamic analysis test. When the cyclic stress F1 is applied to the surface 111 of the new polishing pad 11, a relative reaction force F2 is produced. According to the present preferred embodiment, a pressure sensor (for example, load cell) 13 is installed in the contact probe 12 to measure the reaction force F2.

Thereafter, the tested data and the known polishing characteristics of the new polishing pad 11 are used to establish a matching database.

It is to be understood that, for the sake of simulating a real polishing surfactant behavior, the value of the oscillation frequency for each test can be set subject to the distribution density of the surface asperities of the workpiece to be polished in the simulation. Further, the aforesaid loads include static loads and dynamic loads. The values of static loads are determined subject to the pressure P to be applied to the new polishing pad 11 in the actual polishing process. The values of dynamic loads are determined subject to the average height of the surface asperities of the workpiece to be polished in the simulation. Further, the geometric shape of the aforesaid contact probe 12 can be determined subject to the shape characteristics of the surface asperities of the workpiece to be polished in the simulation. Subject to the aforesaid settings, the simulation is more close to the real operation, improving test accuracy.

After step (A), step (B) is performed as follows, with reference to FIG. 3:

In step (B), prepare a to-be-tested soft polishing pad 13 for polishing a predetermined workpiece (the polishing characteristics and life-span of the to-be-tested soft polishing pad 13 are unknown), and then perform a dynamic analysis test to oscillate the to-be-tested soft polishing pad 13 by a contact probe 12 at a predetermined oscillation frequency and under a predetermined load and apply a cyclic stress F3 to the surface 141 of the to-be-tested soft polishing pad 14 perpendicularly, and then use the same pressure sensor (load cell) 13 to measure the reaction force F4 of the surface 141 of the to-be-tested soft polishing pad 14. It is to be understood that, for the sake of simulating a real polishing surfactant behavior, the value of the oscillation frequency of the dynamic analysis test is set subject to the distribution density of the surface asperities of the workpiece to be polished. The value of the static load or dynamic load is determined in the same manner as step (A).

After step (B), step (C) is finally performed as follows:

In step (C), compare the reaction (the reaction force F4 according to the present preferred embodiment) of the surface 141 of the to-be-tested soft polishing pad 14 with the data of the matching database obtained in step (A), and then predict the polishing characteristics and life-span of the to-be-tested soft polishing pad 14 subject to the comparison result.

Subject to the performance of the aforesaid steps, the polishing characteristics and life-span of the to-be-tested soft polishing pad can be predicted without making an actual polishing test, thereby saving a large amount of time and cost. 

1. A method for predicting the polishing characteristics and life-span of a soft polishing pad, comprising the steps of: (A) preparing a new soft polishing pad having polishing characteristics that are known, and then performing a series of dynamic analysis tests to oscillate said new soft polishing pad with contact probe at different oscillation frequencies and under different loads, and then detecting the surface reaction of said new soft polishing pad during every dynamic analysis test, and then using the tested data and the known polishing characteristics of said new soft polishing pad to establish a matching database; (B) preparing a to-be-tested soft polishing pad for polishing a predetermined workpiece and then performing a dynamic analysis test to oscillate said to-be-tested soft polishing pad at a predetermined oscillation frequency and under a predetermined load and then detecting the surface reaction of said to-be-tested soft polishing pad during the dynamic analysis test; and (C) comparing the surface reaction of said to-be-tested soft polishing pad with the data of said matching database to predict the polishing characteristics and life-span of said to-be-tested soft polishing pad.
 2. The method for predicting the polishing characteristics and life-span of a soft polishing pad as claimed in claim 1, wherein the dynamic analysis tests performed in step (A) and step (B) are to apply a cyclic stress to the surface of said new soft polishing pad or said to-be-tested soft polishing pad perpendicularly when said new soft polishing pad or said to-be-tested soft polishing pad is being oscillated.
 3. The method for predicting the polishing characteristics and life-span of a soft polishing pad as claimed in claim 2, wherein said cyclic stress is applied to the surface of said new soft polishing pad or said to-be-tested soft polishing pad through a contact probe, said contact probe having a geometric shape predetermined subject to the configuration of the surface asperities of said predetermined workpiece.
 4. The method for predicting the polishing characteristics and life-span of a soft polishing pad as claimed in claim 1, wherein detecting the surface reaction of said new soft polishing pad during step (A) and detecting the surface reaction of said to-be-tested soft polishing pad during step (B) are done by means of using a pressure sensor to measure the surface reaction force of said new soft polishing pad and said to-be-tested soft polishing pad.
 5. The method for predicting the polishing characteristics and life-span of a soft polishing pad as claimed in claim 1, wherein the predetermined loads during step (A) and step (B) include static loads and dynamic loads.
 6. The method for predicting the polishing characteristics and life-span of a soft polishing pad as claimed in claim 5, wherein the value of the static load applied during step (B) is determined subject to the pressure to be applied to said to-be-tested soft polishing pad during an actual polishing process.
 7. The method for predicting the polishing characteristics and life-span of a soft polishing pad as claimed in claim 5, wherein the value of the dynamic load applied during step (B) is determined subject to the pressure to the average height of the surface asperities of said predetermined workpiece.
 8. The method for predicting the polishing characteristics and life-span of a soft polishing pad as claimed in claim 1, wherein the value of the oscillation frequency set during step (B) is determined subject to the distribution density of the surface asperities of said predetermined workpiece. 